With the progress in safe driving support and automatic driving technology, the traffic of in-vehicle networks is increasing. In order to handle this, there is a known CAN with Flexible Data-rate (CAN FD) communication system capable of accelerating data transmission and data length extension. In the CAN FD, nodes that perform transmission and reception are typically electronic control units (ECU) as in-vehicle processing devices, and each of the nodes is electrically connected with each other by a bus. A transmission ECU adds an identifier (ID) to communication data to form a message, converts the message into an electric signal to be transmitted onto the bus. Each of the ECUs monitors electric signals on the bus, obtains the ID being used for communication, and identifies the message to be received.
In a case where a plurality of messages is simultaneously transmitted, priority of communication is determined in accordance with the ID. The phase that determines the ECU capable of transmitting the IDs and transmitting the message with the priority is referred to as an arbitration phase. In the arbitration phase, since output is performed simultaneously by a plurality of ECUs, communication is performed at a same speed as the conventional CAN, for example, at 500 kbps. After the ECU that transmits the message is determined by arbitration, the phase proceeds to a data phase for data transmission. The transmission speed in the data phase in which one specified ECU performs output is 2 Mbps, for example.
This, however, would cause a problem of failure in correct data transmission due to effects of reflection generated when the communication speed is increased to 2 Mbps in a conventional network configuration enabling communication at 500 kbps. As a method for removing noise due to the reflection, there is a known configuration including a filter circuit that removes noise and a resistor that allows a current to flow through the filter circuit (for example, refer to PTL 1).